There are several airless paint and coating solution sprayers on the market and these work very well and are reliable with several types of coatings such as water-base coatings or organic base coatings, epoxides, etc. However, these known spraying apparatus are not reliable and are in fact troublesome and require frequent maintenance when the solution is a binder solution having suspended particles which are non-abrasive, such as zinc particles in a cold galvanizing solution for coating steel products which are prone to the formation of oxidation (rust). Usually, when known prior art pumps are used to spray such solution, they fail within one hour of usage due to the particles in the solution. These pumps are piston pumps and their packing quickly deteriorates. Also, they use ball-type check valves and the particles accumulate under the action of pressure in the area of these check valves and they become inoperative requiring replacement parts and/or cleaning.
Another disadvantage of known prior art spraying apparatus is that when they use binder solution with suspended particles, the suspended particles have a tendency of settling into the solution when maintained stagnant for short periods of time and heavier particles settle to the bottom of the buckets containing such solution. Accordingly, the solution sprayed is not a homogeneous solution and this is also problematic.